The frame rate is the number of frames that are rendered per second. For example, movie film is shot at 24 frames per second (fps), while NTSC analog video is shot at 29.97 interlaced fps.
Input lag is the delay between pressing a button and seeing the result on-screen, aim to keep it under 50ms. Frame drops are sudden decreases in frame rate caused by increased load on components.
IGN has released fifteen minutes of gameplay footage from Bloodborne running on the PS5 Pro. The image quality does seem sharper than its base PS4 counterpart, though it still runs at an uneven 30fps.